Identification of Harman as the Antibiotic Compound Produced by a Tunicate-Associated Bacterium

The alkaloid harman, previously reported from some marine invertebrates, was identified as the antibiotic substance of the tunicate-associated bacterium Enterococcus faecium. It exhibited antibacterial activity (MIC, 0.017 mM) against the ichthyopathogenic strain Vibrio anguillarum.     

Monitoring changes in anthocyanin and steroid alkaloid glycoside content in lines of transgenic potato plants using liquid chromatography/mass spectrometry

Transgenic potato plants overexpressing and repressing enzymes of flavonoids biosynthesis were created and analyzed. The selected plants clearly showed the expected changes in anthocyanins synthesis level. Overexpression of a DNA encoding dihydroflavonol 4-reductase (DFR) in sense orientation resulted in an increase in tuber anthocyanins, a 4-fold increase in petunidin and pelargonidin derivatives. A significant decrease in anthocyanin level was observed when the plant was transformed with a corresponding antisense construct. The transformation of potato plants was also accompanied by significant changes in steroid alkaloid glycosides (SAG) level in transgenic potato tuber. The changes in SAGs content was not dependent on flavonoid composition in transgenic potato. However, in an extreme situation where the highest (DFR11) or the lowest (DFRa3) anthocyanin level was detected the positive correlation with steroid alkaloid content was clearly visible. It is suggested that the changes in SAGs content resulted from chromatin stressed upon transformation. A liquid chromatography/mass spectrometry (LC/MS) system with electrospray ionization was applied for profiling qualitative and quantitative changes of steroid alkaloid glycosides in tubers of twelve lines of transgenic potato plants. Except alpha-chaconine and alpha-solanine, in the extracts from dried tuber skin alpha-solamargine and alpha-solasonine, triglycosides of solasonine, were identified in minor amounts, triglycosides of solanidine dehydrodimers were also recognized.     

Biosynthesis of calystegines: 15N NMR and kinetics of formation in root cultures of Calystegia sepium

Calystegines are nortropane alkaloids bearing between three and five hydroxyl groups in various positions. [15N]Tropinone was administered to root cultures of Calystegia sepium and the incorporation into calystegines was followed. Increase of label in calystegines was measured by one-dimensional 15N NMR and inverse-detected 2D NMR techniques. The results show that tropinone and pseudotropine are metabolites in the biosynthetic pathway of calystegines. The velocity of calystegine accumulation was followed kinetically by transfer of root cultures from 15N-enriched medium to 14N-medium and analysis by GC-MS. A constant calystegine formation with no interference by excretion or degradation was observed. A biosynthetic rate for individual calystegines at each time point was calculated, the maximum was 0.4 mg/day/g of biomass. This allowed the velocity of individual biosynthetic steps to be estimated.     

QTL mapping of foliar glycoalkaloid aglycones in Solanum tuberosum×S. berthaultii potato progenies: quantitative variation and plant secondary metabolism

 Glycoalkaloids are quantitatively inherited in Solanum, and in high concentrations they can be toxic to humans. The increased use of wild potato germplasm to improve the pest resistance, yield, and quality characteristics of cultivated potato may elevate or introduce new, more toxic glycoalkaloids into the cultivated gene pool. Therefore, it is important to increase our understanding of their inheritance, accumulation, and biosynthesis. Glycoalkaloids have two basic constituents – a glycosidic grouping and a steroid alkaloid skeleton. Steroid alkaloids are classified as solanidanes and spirosolanes, of which solanidine and solasodine are, respectively, representatives. RFLP-mapped, diploid, reciprocal backcross potato progenies involving the parents S. tuberosum and S. berthaultii, which produce solanidine and solasodine, respectively, were analyzed for segregation of the glycoalkaloids solanine, chaconine, solasodine and solamargine to identify quantitative trait loci (QTLs) for the production of the aglycones solanidine and solasodine. The F₁ clone M200-30 exhibited low to nondetectable levels of solasodine and solanidine, suggesting that expression was controlled by recessive genes. In a backcross to berthaultii (BCB) and backcross to tuberosum (BCT), several QTLs for the accumulation of solasodine and solanidine were identified. Three QTLs explaining approximately 20% of the variation in solasodine were identified in BCB on chromosomes 4, 6, and 12. Similarly, three QTLs were identified in BCT on chromosomes 4, 8 and 11, but these accounted for only 10% of the variation observed in solasodine accumulation. Two QTLs for solanidine were identified in BCT on chromosomes 1 and 4. The QTL located on chromosome 1 was highly significant, accounting for 17% and 22% of the variation in solanidine accumulation in 1994 and 1995, respectively. This same QTL was also detected in BCB. The QTLs detected in this study probably represent structural and/or regulatory genes controlling the accumulation of solasodine and solanidine. Results are discussed in the context of steroid alkaloid accumulation and biosynthesis. Received: 27 August 1997 / Accepted: 16 March 1998     

Fast screening method for benzophenanthridine alkaloids in plant cell cultures of California poppy using a dansyl-glycine-β-cyclodextrin molecular recognition system

The association constant K for the host-guest complex comprised of sanguinarine/dansyl-glycine--cyclodextrin was found to be 5.75 × 105 M. The sensitivity factor(), which is defined as the ratio of the change of the fluorescence intensity after complex formation to the intensity of free, uncomplexed dansyl-glycine--cyclodextrin, showed an almost linear dependence on analyte concentration up to 50M sanguinarine. This molecular recognition system can be exploited to rapidly estimate the total concentration of benzophenanthridine alkaloids in suspension cultures of Eschscholtzia californica. © Rapid Science Ltd. 1998     

Unusual C19-diterpenoid alkaloids from Aconitum vilmorinianum var. patentipilum

Three new C₁₉-diterpenoid alkaloids vilmotenitines A-C (1-3), together with seven known ones, vilmorine D (4), talatizidine (5), isotalatizidine (6), vilmorrianine B (7), vilmorrianine D (8), talatizamine (9), 8-deacetyl-yunaconitine (10), were isolated from Aconitum vilmorinianum var. patentipilum. Vilmotenitines A (1) and B (2) are the second natural occurrences of C₁₉-diterpenoid alkaloids with a unique rearranged six-membered B ring formed by the C₍₈₎–C₍₁₀₎ linkage.     

Translocation and accumulation of nicotine via distinct spatio-temporal regulation of nicotine transporters in Nicotiana tabacum

In plants, secondary metabolites play important roles in adaptation to the environment. Nicotine, a pyridine alkaloid in Nicotiana tabacum, functions as chemical barrier against herbivores. Nicotine produced in the root undergoes long-distance transport and accumulates mainly in the leaves. Since production of such defensive compounds is costly, plants must regulate the allocation of the products to their tissues; however, the molecular mechanism of nicotine translocation remains unclear. Our recent studies identified a novel multidrug and toxic compound extrusion (MATE)-type nicotine transporter, JAT2 (jasmonate-inducible alkaloid transporter 2). This transporter is specifically expressed in leaves, localizes to the tonoplast, and transports nicotine as its substrate. The specific induction of JAT2 expression in leaves by methyl jasmonate (MeJA) treatment suggests that this transporter plays an important role in nicotine distribution to leaves, especially under herbivore attack, by transporting nicotine into the vacuole. Considering JAT2, together with the previously identified MATE transporters JAT1, MATE1, and MATE2, and the PUP (purine permease) transporter NUP1 (nicotine uptake permease1), we show a model of nicotine translocation and accumulation via distinct spatio-temporal regulation of nicotine transporter expression. Furthermore, we discuss the possible role of nicotine transporters in determining outcrossing rates and seed production.     

长序虎皮楠果实中的一个新的生物碱（英文）

从长序虎皮楠（Daphniphyllum longeracemosum）果实的甲醇提取物中分离得到一个新的虎皮楠生物碱和三个已知的环烯醚萜苷型虎皮楠生物碱。通过现代波谱解析技术鉴定为daphlongeranine F（1）,caldaphnidine F（2）,daphcalycinosidine B（3）and daphcalycinosidine C（4）。其中,三个环烯醚萜苷虎皮楠生物碱系首次从该种分离得到。     

Knockdown of berberine bridge enzyme by RNAi accumulates (<Emphasis Type="Italic">S</Emphasis>)-reticuline and activates a silent pathway in cultured California poppy cells

Reticuline is a key compound in the biosynthetic pathway for isoquinoline alkaloids in plants, which include morphine, codeine and berberine. We established cultured California poppy (Eschscholzia californica) cells, in which berberine bridge enzyme (BBE) was knocked down by RNA interference, to accumulate the important key intermediate reticuline. Both BBE mRNA accumulation and enzyme activity were effectively suppressed in transgenic cells. In these transgenic cells, end-products of isoquinoline alkaloid biosynthesis, such as sanguinarine, were considerably reduced and reticuline was accumulated at a maximum level of 310 μg/g-fresh weight. In addition, 1 g-fresh weight of these cells secreted significant amounts of reticuline into the medium, with a maximum level of 6 mg/20 mL culture medium. These cells also produced a methylated derivative of reticuline, laudanine, which could scarcely be detected in control cells. We discuss the potential application of RNAi technology in metabolic modification and the flexibility of plant secondary metabolism.     

Spermatinamine, the first natural product inhibitor of isoprenylcysteine carboxyl methyltransferase, a new cancer target

Isoprenylcysteine methyltransferase (Icmt) catalyzes the carboxyl methylation of oncogenic proteins in the final step of a series of post-translational modifications. The inhibition of Icmt provides an attractive and novel anticancer target. A natural product high-throughput screening campaign was conducted to discover inhibitors of Icmt. The Australian marine sponge, Pseudoceratina sp., yielded spermatinamine, a novel alkaloid with a bromotyrosyl-spermine-bromotyrosyl sequence, as the bioactive constituent. Its structure was determined by 1D and 2D NMR spectroscopy. Spermatinamine is the first natural product inhibitor of Icmt.